In computer networks, a network device may be connected to one or more network devices via two or more physical links. The term “link” is often used to refer to the connection between two devices on a network. The link may be a physical medium, such as a copper wire, a coaxial cable, any of a host of different fiber optic lines, or a wireless connection. In addition, network devices may define “virtual” or “logical” links, and map the virtual links to the physical links. In some cases, these two or more links may be logically grouped or aggregated together to form an “aggregated bundle.” For example, one or more routers may be connected to a customer edge device via an aggregate bundle of multiple physical links. In some cases, Ethernet links may be combined into one logical interface for higher bandwidth and redundancy. Ports of the Ethernet links that are combined in this manner are referred to as a link aggregation group (LAG) or bundle.
Generally, link aggregation may provide connection redundancy. That is, should one of the links of the aggregated bundle fail, the network device may begin sending traffic to the other network device across the non-failed links of the aggregated bundle, thereby providing redundancy in the form of redundant links for delivery of traffic between two devices.
In one example, a customer network site may be given redundant connectivity to a network through multiple provider edge (PE) network devices (e.g., routers, switches, etc.). This form of redundancy is referred to as “multi-homing.” In one type of multi-homing, referred to as “active-active” multi-chassis link aggregation (MC-LAG) configuration, each of the PE devices is configured to actively forward traffic and the multiple, physical links providing the multi-homed connectivity are logically aggregated and treated as a single, logical link. In MC-LAG configured networks, MC-LAG enables a customer edge (CE) network device to form a logical LAG interface between two MC-LAG peer nodes. MC-LAG provides, for example, redundancy and multi-homing support for the MC-LAG peer nodes.
An Ethernet Virtual Private Network (EVPN) may be used to extend two or more remote layer two (L2) customer networks through a core layer three (L3) network (usually referred to as a provider network or core network), in a transparent manner, i.e., as if the L3 network does not exist. In particular, the EVPN transports L2 communications, such as Ethernet packets or “frames,” between customer networks via traffic engineered label switched paths (LSP) through the core network in accordance with one or more multiprotocol label switching (MPLS) protocols. In a typical configuration, PE devices coupled to the CE network devices of the customer networks define label switched paths (LSPs) within the provider network to carry encapsulated L2 communications as if these customer networks were directly attached to the same local area network (LAN). In some configurations, the PE devices may also be connected by an IP infrastructure in which case IP/GRE tunneling or other IP tunneling can be used between the network devices.
In an EVPN, L2 address learning (also referred to as “MAC learning”) on a core-facing interface of a PE device occurs in the control plane rather than in the data plane (as happens with traditional bridging) using a routing protocol. For example, a PE device typically uses the Border Gateway Protocol (BGP) (i.e., an L3 routing protocol) to advertise to other PE devices the MAC addresses learned from the local consumer edge network devices to which the PE device is connected. As one example, a PE device may use a BGP route advertisement message to announce reachability information for the EVPN, where the BGP route advertisement specifies one or more MAC addresses learned by the PE device instead of L3 routing information. Additional example information with respect to EVPN is described in “BGP MPLS-Based Ethernet VPN,” Request for Comments (RFC) 7432, Internet Engineering Task Force (IETF), February, 2015, the entire contents of which are incorporated herein by reference.
VXLAN provides a tunneling scheme to overlay L2 networks on top of L3 networks. VXLANs establish tunnels for communicating traffic, e.g., L2 broadcast, unknown unicast, and multicast (BUM) packets, over common physical IP infrastructure between the PE devices. That is, VXLAN overlay networks are designated for each customer network and operated over the existing LAN infrastructure of the data center. Devices that support VXLANs are called virtual tunnel endpoints (VTEPs) (also known as “VXLAN tunnel endpoints”)—VTEPs can be end hosts or network switches or routers. VTEPs encapsulate VXLAN traffic and de-encapsulate that traffic when it leaves the VXLAN tunnel. Additional example information with respect to VXLAN is described in “Virtual eXtensible Local Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks,” Request for Comments (RFC) 7348, August 2014, the entire contents of which are incorporated herein by reference.
EVPN enables connecting customer sites using Layer 2 virtual bridges. VXLANs enable extending a Layer 2 connection over an intervening Layer 3 network while providing the network segmentation a VLAN provides, but without the scaling limitation of traditional VLANs. EVPN with VXLAN encapsulation may in this way improve Layer 2 connectivity in a multi-tenant environment. EVPN may be used to provide a network virtualization overlay (NVO) solution using VXLAN or Network Virtualization using Generic Routing Encapsulation (NVGRE) for tunnel encapsulation over an IP core network that provides IP connectivity between NVO endpoints (NVEs). Further example structural and functional details of an EVPN network overlay are described in “A Network Virtualization Overlay Solution using EVPN,” draft-ietf-bess-evpn-overlay-04, Internet Engineering Task Force (IETF), Jun. 10, 2016, the entire contents of which are incorporated herein by reference.